The heat generated by the internal components of electronic devices has long been a significant factor determining the design of microelectronic systems. Semiconductors typically have a threshold temperature above which their performance is severely degraded, thus the internal cooling of electronic equipment has been a parameter of great interest to designers and manufacturers. Some common forms of heat dissipation in early electronics designs were liquid to gas phase change of a fluid in direct contact with the heat-generating device (Camp, in U.S. Pat. No. 2,883,591; April 1959), metal-to-metal contact heat conduction away from the heat-generating components (Deakin, in U.S. Pat. No. 2,917,286; December 1959), a heat sink in direct thermal contact with the mechanical structure of the device (Potter, et al. in U.S. Pat. No. 3,196,317; July 1965), and solid to liquid phase change of a substance in thermal contact with the heat-generating device (Haumesser, et al. in U.S. Pat. No. 3,328,642; June 1967).
The most common forms of heat dissipation in early personal computer designs involved direct physical contact between heat-generating integrated circuits and a heat-conducting heat sink mass such as aluminum, and non-turbulent airflow, typically generated by electrical fans, to circulate cool air through a space interior to the computer system housing. In the early large-scale computing systems of the 1940s and 1950s, heat dissipation consisted primarily of ventilation apertures in housings, followed by ambient-air fans and blowers which cooled by forced air convection.
Zelina, in U.S. Pat. No. 3,566,958 (1971), describes a means of thermally coupling heat conductors to integrated circuit chips, though without addressing how to transport the heat contained in the heat-conducting material away from the space surrounding the electrical device. In U.S. Pat. No. 3,648,113 (1972) Rathjen describes a means of stacking planar electronic devices, with spacing between the flat planes, and cooling the entire assembly using fluid flow across the flat surfaces; the cooling fluid exits the entire assembly, thereby transporting heat away from the heat-generating electronics. Schuler discloses an electronics system casing with good thermal conduction properties in U.S. Pat. No. 3,699,394 (1972); the case was presumed to be of metallic composition, though possibly sealed or bonded with thermally conductive epoxy. Austin, in U.S. Pat. No. 3,737,728 (1973) discloses a mounting structure for fragile heat-generating devices (e.g. devices used in computer apparatuses), as well as uniformity of heat conduction and good heat dissipation away from the core assembly area. These ideas are combined in U.S. Pat. No. 3,865,183 (1975), in which Roush describes a more comprehensive means of constructing a full computer assembly with good heat dissipation characteristics of the individual circuit boards in the module, with fluid flow for removal of heat energy from the assembly.
As demand for ruggedized portable electronic devices increased, engineers began to incorporate shock and vibration damping features into electronic system designs. Damping of vibration and shock forces is particularly important for hard disk drives (magnetic spinning platter disk drives) which are susceptible to externally generated vibrations and shocks that may cause a read head to make physical contact with a spinning surface, thereby rendering unreadable the information contained in that physical portion of the platter surface. Damping of internally generated kinetic forces that result in vibration is important for reliable operation of hard disk drives and collections of hard disk drives that are mounted in the same enclosure.
U.S. Pat. No. 4,382,587 (Heinrich, et al, May 1983) disclose a means for vibration damping for an electronic component and system designs. U.S. Pat. No. 6,618,246 (Sullivan et al., September 2003) disclose a design that incorporates thermal conduction and shock resistance in distinctive features for an electronic unit. U.S. Pat. No. 8,050,028 (Merz et al., November 2011) disclose a design that incorporates thermal conduction and shock resistance in distinctive features for a computing device. U.S. Pat. No. 8,199,506 (Janik et al., June 2012) disclose a design for thermal conduction and shock resistance for a solid state data storage assembly. U.S. Pat. No. 8,913,390 (Malek et al., December 2014) disclose a design for thermal conduction and shock resistance at the edge surface of a printed circuit board. U.S. Pat. No. 6,151,216 (Vos et al., November 2000) disclose a design that incorporates thermal conduction and shock and vibration resistance in the same feature by using a wire rope connected to both a housing and an enclosed electronic device. U.S. Pat. No. 8,520,390 (Okamoto et al., August 2013) disclose a design that incorporates thermal conduction and vibration damping for an electro-mechanical device using two separate materials with distinctive characteristics.
Despite heat dissipation innovations for electronic devices in general, the hard disk drive (magnetic spinning platter disk drive) is a computer component that continues to accomplish low-efficiency heat dissipation primarily by means of air circulation around the exterior of the disk drive unit. Such a hard disk drive unit is a data storage device used for storing and retrieving digital information using rapidly rotating disks (platters) coated with magnetic material. Digital information is written to and read from the rotating disks by means of a sensor on a mechanical arm that is literally flown over the surface of the disk. The atmospheric environment inside the disk drive unit is critical to the “fly-height” of the sensor. Therefore, almost all hard disk drive units are designed to allow atmospheric air to enter and leave the unit as necessary to maintain a suitable molecular composition and pressure of gas inside the disk drive unit. Because the hard disk drive units a) must remain open to the atmosphere and b) produce rotational and translational vibration that must be damped for proper operation, disk drive units commonly use air circulation around the exterior of the disk drive unit for heat dissipation. Two major exceptions to the common hard disk drive design exist in the market today—the SSD and the helium filled hard disk drive. The SSD is a “solid-state disk” that is comprised of solid state memory chips and has no moving parts. The helium filled hard disk drive unit is a hermetically sealed unit designed to internally contain a helium environment instead of atmospheric air. Examples of a helium filled hard disk drive unit are produced by HGST and Seagate. All disk drive units can benefit greatly from an improved means of heat dissipation that results in improved performance, reliability, and disk drive unit longevity. Optical platter disk drives are subject to many of the same limitations as magnetic spinning platter disk drives.
Current solutions for electronic device mounting and enclosures that combine vibration damping with heat dissipation have significant shortcomings. Typically, current solutions for electronic device mounting and enclosures are optimized for only one of a) manufacturing cost, b) thermal transfer, or c) vibration damping. The solutions that are low in manufacturing costs are typically air-cooled and result in marginal cooling and vibration damping performance. The solutions that are optimized for thermal transfer are typically constructed as custom cold-plate designs with tight tolerances and complex cooling piping that result in higher manufacturing costs, higher system maintenance costs, and lower vibration damping. The solutions that are optimized for vibration damping are typically air-cooled and require moderately complex structural elements resulting in marginal cooling performance, larger overall unit sizes, and higher manufacturing costs. The solutions that are optimized for vibration damping and heat dissipation are typically constructed with complex structural elements resulting in larger overall unit sizes, and higher manufacturing costs, and higher system maintenance costs. For example, the heat-conducting wire rope solution of U.S. Pat. No. 6,151,216 requires attachment points for the wire rope on both the exterior casing or chassis and the electronic device itself. A failure of either attachment point, or a fatigue failure of the wire rope itself after prolonged exposure to small-scale vibrations, causes loss of both heat conduction and vibration damping functionality.
Thermally conductive plastics and elastomers are newer marketplace innovations that enable excellent thermal conduction, mechanical strength, and vibration damping properties in a single material and are useful for such applications as heat exchangers, heat sinks, enclosures, and electronics substrates and packaging. Two examples of potential commercial applications of thermally conductive plastics are disclosed in U.S. Patent Application US20100012354 A1 (2009), in which Hedin and Miller describe a printed circuit board contains a thermally conductive dielectric layer; and Patent Application WO2013171483 A1 (2012), in which Lee and Laverick disclose a vessel of thermally conductive plastic for freeze-drying.
The inventions disclosed herein overcome many of the shortcomings of prior art in relation to the heat dissipation and vibration damping of electronic devices. Thermally conductive polymers enable significant design improvements as disclosed herein. In particular, mounting assemblies can be constructed using thermally conductive polymers with low cost manufacturing techniques that create assemblies that are in contact with and interposed between the electronic device to be cooled and the supporting structure for the electronic device. This contact type of assembly transmits heat as much as one hundred times more efficiently than air while at the same time effectively absorbing vibrations and shock that would normally act on the electronic device or be passed on to the supporting structure. This is a significant improvement on current processes, eliminating or greatly reducing the requirement for inefficient air exchange cooling and thereby enabling the installation of electronic devices in a sealed enclosure. These improvements result in lower manufacturing costs as well as electronic device performance improvements that include longer life, higher reliability, and lower maintenance. Further, this is an enabling improvement for the systems in which the devices are installed resulting in higher system density designs, smaller system size, lower manufacturing costs, higher environmental tolerances, lower maintenance costs, more flexibility in installation locations, better control of system heat dissipation, lower operational noise, and much higher physical, electrical, and magnetic system security.